11 2 Probability and Punnett Squares Slide 1

11 -2 Probability and Punnett Squares Slide 1 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Genetics and Probability The likelihood that a particular event will occur is called probability. Slide 2 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Punnett squares can be used to predict and compare the genetic variations that will result from a cross. Slide 3 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares A capital letter represents the dominant allele. A lowercase letter represents the recessive allele. In this example, T = tall t = short Slide 4 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Gametes produced by each F 1 parent are shown along the top and left side. Slide 5 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Possible gene combinations for the F 2 offspring appear in the four boxes. Slide 6 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Organisms that have two identical alleles for a particular trait are said to be homozygous(pure). Organisms that have two different alleles for the same trait are heterozygous(hybrid). Slide 7 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares All of the tall plants have the same phenotype, or physical characteristics. The tall plants do not have the same genotype, or genetic makeup. One third of the tall plants are TT, while two thirds of the tall plants are Tt. All of the short plants are tt. Slide 8 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares The plants have different genotypes (TT and Tt), but they have the same phenotype (tall). TT Homozygous Tt Heterozygous Slide 9 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Probability and Segregation 1/4 are TT. 1/2 are Tt 1/4 are tt. Slide 10 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Probability and Segregation Because (T) is dominant over (t), 3/4 of the F 2 plants should be tall. The ratio of tall plants (TT or Tt) to short (tt) plants is 3: 1. Slide 11 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Genetics Problems Dominance/Recessive Slide 12 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Assume white color is dominant over yellow in squash. If pollen from the anther of a heterozygous white plant is placed on the pistil of a yellow plant, show the genotypes and phenotypes of the offspring of this cross. Slide 13 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares Brown eyes is dominant over blue eyes. A brown-eyed man whose father was brown and mother was blue married a blue-eyed women whose parents were both brown eyed. The couple had a blue eyed son. Draw a pedigree chart showing the genotypes and phenotypes of all the individuals indicated. List all possible genotypes for people you cannot be sure of. Slide 14 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares In humans, normal pigmentation is due to a dominant gene and albinism to a recessive allele. A normal man marries an albino women and their first child is albino. What are the genotypes of the 3 people? If they have several children, what possible genotypes and phenotypes can result and in what proportions? Slide 15 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability and Punnett Squares When two green seed pea plants are crossed we get 385 green seed plants and 115 yellow seed plants. When the yellow seed plants are crossed with the original parent plants we get 975 green seed plants and 1010 yellow seed plants. What are the genotypes of the parents from the P 1 cross? Slide 16 of 21 Copyright Pearson Prentice Hall End Show

11 -2 Probability can be used to predict a. average outcome of many events. b. precise outcome of any event. c. how many offspring a cross will produce. d. which organisms will mate with each other. Slide 17 of 21 End Show Copyright Pearson Prentice Hall

11 -2 Compared to 4 flips of a coin, 400 flips of the coin is a. more likely to produce about 50% heads and 50% tails. b. less likely to produce about 50% heads and 50% tails. c. guaranteed to produce exactly 50% heads and 50% tails. d. equally likely to produce about 50% heads and 50% tails. Slide 18 of 21 End Show Copyright Pearson Prentice Hall

11 -2 Organisms that have two different alleles for a particular trait are said to be a. hybrid. b. heterozygous. c. homozygous. d. recessive. Slide 19 of 21 End Show Copyright Pearson Prentice Hall

11 -2 Two F 1 plants that are homozygous for shortness are crossed. What percentage of the offspring will be tall? a. 100% b. 50% c. 0% d. 25% Slide 20 of 21 End Show Copyright Pearson Prentice Hall

11 -2 The Punnett square allows you to predict a. only the phenotypes of the offspring from a cross. b. only the genotypes of the offspring from a cross. c. both the genotypes and the phenotypes from a cross. d. neither the genotypes nor the phenotypes from a cross. Slide 21 of 21 End Show Copyright Pearson Prentice Hall